1. Field of the Technology
This present application relates generally to memory devices such as magnetic random access memories (MRAMs), and more particularly to memory devices having ferromagnetic structures with perpendicular magnetic anisotropy which exhibit varying extraordinary Hall effect resistances, and also relates generally to programmable and reconfigurable logic devices having ferromagnetic structures with perpendicular magnetic anisotropy which exhibit the extraordinary Hall effect.
2. Description of the Related Art
Non-volatile magnetic random access memories (MRAMs) have been proposed as candidates to replace conventional dynamic random access memories (DRAMs) and hard disk drives. Such memory devices make use of GMR and tunneling magnetoresistance (TMR) sensing techniques. Currently-proposed MRAM devices utilize two magnetic layers which are magnetized in-plane so that variations in the GMR and/or TMR may be measured. The magnetic layers have magnetic orientations which are either in parallel or opposite each other, which create four magnetic states and give rise to two different GMR or TMR resistances associated with bits ‘0’ and ‘1’. There is a need, however, for increased data storage capacity in these types of memory structures.
A conventional logic device may be included in a circuit called a field programmable gate array (FPGA), which is one type of programmable logic device (PLD). FPGAs use a grid of logic gates similar to that of an ordinary gate array, but the programming is performed by the customer, not by the manufacturer. FPGAs are typically programmed after being soldered down to a circuit board. In most larger FPGAs, the configuration is volatile and must be reloaded into the device whenever power is applied or different functionality is required.
Most any PLD includes a combination of one or more logic devices and memory devices. The memory device is used to store a pattern that was provided on the integrated circuit (IC) during programming. Most of the methods for storing data in the IC have been adapted for use in PLDs. These include silicon antifuses, electrically programmable read-only memory (EPROM) or EEPROM cells, Flash memory, and static random access memory (SRAM). An EPROM cell is a metal-oxide semiconductor transistor that may be switched on by trapping an electric charge permanently on its gate electrode. The charge remains for many years but may be removed by exposing the chip to strong ultraviolet light in a device called an EPROM eraser. Flash memory is non-volatile, retaining its contents even when the power is switched off. It may be erased and reprogrammed as required, which makes it useful for PLD memory. SRAM is a volatile type of memory, meaning that its contents are lost each time the power is switched off.
Referring ahead to FIG. 22, an SRAM device 1200B is shown to include a plurality of look-up tables (LUTs) of memory (such as an LUT 1202B) and a plurality of switches (such as a switch 1204B). SRAM-based PLDs are dynamic and adaptive, being programmable “on-the-fly” to new requirements as needed. SRAM-based PLDs must be programmed every time the circuit is switched on, which is usually performed automatically by another part of the circuit.
Proposals have been made to use magnetic devices (such as Giant Magnetoresistive (GMR) and tunneling magnetoresistance (TMR)-based structures) to replace conventional semiconductor logic devices. For example, proposals relating to non-volatile magnetic RAM (MRAM) are described in JP876674 to W. C. Black, U.S. Pat. No. 6,779,168, and U.S. Pat. No. 6,774,391. Proposed magnetic PLDs utilize two magnetic layers which are magnetized in-plane so that variations in the GMR and/or TMR may be measured. The magnetic layers have magnetic orientations which are either in parallel or opposite each other, which create four possible states but give rise to only two different GMR or TMR resistances associated with bits ‘0’ and ‘1’. In addition, a writing process is necessary in order to program a different logic operation, which increases power dissipation for operation. Thus, what are also needed are structures for simpler logic devices and circuits to overcome the deficiencies of the prior art.